1. Field of the Invention
The present invention relates to a Universal Serial Bus (USB) composite device, and in particular relates to a USB hub capable of supplying power to a USB device, and a method thereof.
2. Description of the Related Art
The USB interface is an industry standard developed in the mid-1990s that supports data exchange between a USB host and a wide range of simultaneously accessible USB devices. The USB devices can be attached to the USB host through a USB hub. The attached USB devices share USB bandwidth through a host-scheduled, token-based protocol. The USB interface allows the USB devices to be attached, configured, used, and detached while the USB host and other USB devices are in operation.
Conventionally, a USB host may provide power to USB devices connected thereto during the USB host is in a working power state. Nevertheless, the USB host stops providing power to the connected USB devices when the host becomes inactive. Accordingly, there is a need to provide power for USB devices when the USB host is in an inactive state, e.g., through providing a power management device and method to supply an alternate power independent of the host power.